The present invention relates generally to a new composition comprising a combination of water-soluble polymers and intended for sizing the warps of textile yarns and, especially, polyester yarns and to a process for obtaining such textile sizing compositions.
The invention further pertains to an advantageous process for sizing textile yarns, preferably in an aqueous medium, utilizing the compositions of the invention and to the resultant abrasion resistant yarns suitable for weaving.
In the textile industry, there is an increasing tendency to abandon the prior practice of providing textile yarns with an abrasion resistance which is sufficient for weaving, by applying a high degree of twist to the continuous yarn, of the order of several hundred turns per meter due to a great extent to the high manufacturing costs involved in generating this twist.
Attempts have therefore been made to at least in part replace the degree of twist required by applying to the yarn a sizing whose strength increases proportionately as the twist of the yarn is reduced. At present, a minimum twist of 10 to 15 turns per meter, applied solely by the spinning frame, has been attained. However, these early developed sizing products proved inadequate for imparting an abrasion resistance to the yarn emerging from the spinning frame sufficient to permit weaving under satisfactory conditions.
Furthermore, in recent years an increase in the speed of weaving looms has been attained from 250 to 350 strokes per minute with the result that the warp yarns are subjected to even greater frictional stresses and, accordingly, it has become necessary to employ high performance sizing compositions to achieve satisfactory weaving of such yarns.
Acrylic and/or vinyl homopolymers or copolmers have been recommended as suitable sizing products. However, experience has shown that they are not suitable for the sizing of all textile yarns; in particular, their adhesion to polyester type yarns is poor, and therefore these yarns are not protected adequately to withstand subsequent weaving operations.
Moreover, given the increased speed of current weaving looms, yarn slippage and breakage are observed repeatedly resulting in a reduction in the loom output with yarns treated with such prior art sizing compositions.
It is also known from French Patent No. 2,192,133 and its Certificate of Addition No. 2,213,302 and from U.S. Pat. No. 4,150,946 that it is possible to employ, sulfonated polyesters or anionic polyester-urethanes especially for sizing polyester yarns. These polymers have very good sizing properties for polyester yarns with the result that the weaving conditions and output are excellent. Nevertheless, these products are still not entirely satisfactory when employed for section sizing because it has been found that the individual yarns stick to each other on the beam.
An improved sizing composition, described in French Patent No. 2,291,314 has been proposed, which is in the form of an emulsion or of an aqueous dispersion comprising from 60 to 90% by weight of an acrylo-vinyl copolymer and from 40 to 10% by weight of a water-soluble polyester. The warp yarns sized with the aid of the foregoing composition have good abrasion resistance during subsequent weaving operations and no slippage or breakage of the yarns are observed, nor fouling of the weaving looms.
However, these compositions still suffer from the disadvantage that they can only effectively be removed by means of an organic solvent (usually trichloroethylene) because of their insolubility in water which, in turn, causes additional technological problems due to the toxicity of the solvent, which is particlarly true with respect to trichloroethylene, and due to the need to further provide a recovery unit for such solvents.